Gene Delivery Using Chemical Methods - Challenges in Delivery of Therapeutic Genomics and Proteomics - page 159

of pcTG37 was synthesized, which displayed high transfection efficiency in vitro and
in vivo [221] .
It was demonstrated that transfection efficiency was related to structure and geom-
etry of the polyamine and the nature of the spacer and lipid. A series of linear poly-
amines (primarily spermine or spermidine derivatives) linked via amide bond to a
hydrophobic group such as cholesteryl carbamate, fatty alcohols, or fatty acids were
introduced ( Fig. 4.13 ) [222,223] . Few compounds of this family demonstrated higher
transfection activity against pulmonary epithelium CFT1 cells in vitro as compared
to (1,2-dimyristyloxypropyl-3-dimethyl-hydroxyethyl ammonium bromide) DMRIE
or DC-Chol. However, these in vitro results do not correlate with in vivo transfec-
tion activity in BALB/c mouse lungs. One of the compounds with fatty alcohol as a
hydrophobic anchor displayed the highest transfection activity on the CFT1 model
but was not effective in the BALB/c mouse lung model. In an opposite case, com-
pound with cholesteryl carbamate as a hydrophobic anchor demonstrated lower in
vitro activity on CFT1 cells and displayed the highest level of gene expression in the
BALB/c mouse lung model. In the BALB/c mouse lung model, T-shaped polyamines
were found to be more effective than their linear-shaped counterparts. In addition,
cholesteryl derivatives demonstrated higher transfection efficiency in comparison
with their double-chain lipids counterparts. Biophysical characteristics of this family
of cationic lipid-DNA complexes were reported explicitly [224] .
In another study, a carbamoyl group was used as the linker between the polyamine
head and vitamin D2/3-based hydrophobic anchor, resulting in biocompatible cat-
ionic lipids A, B, and C that were evaluated for their transfection efficiency against
Lewis lung carcinoma 3LL, BL-6, NIH3T3, 293, and Hela cells, when coformulated
with DOPE in the molar ratio of 1:1 ( Fig. 4.14 ) [225] . The compounds exhibited
superior transfection activity in BL-6 cells as compared with DC-Chol/DOPE stan-
dard lipid.
Uses of amino acid or peptide-based spacers to connect the polyamine head with
the hydrophobic tail were explored [226]. The synthesized compounds were tested
in vitro for their transfection activity, against COS-7, SNB-19, and C8161 cell lines
with or without the use of helper lipids. Few compounds of the family were found
to be more effective in vitro than the standard established transfection vectors like
Transfectan TM , Lipofectamine TM , and Lipofectin TM . Oligo-ornithine analogues were
proposed as an efficient transfecting agent [227,228] . The oligo-ornithine analogues
displayed comparable or higher transfection efficiency against mouse embryonic
fibroblast NIH3T3, HepG2, and 293T cell lines when coformulated with DOPE as
compared to standard DC-Chol/DOPE, Lipofectin TM . In addition, a new method of
solid-phase organic synthesis (SPOC) to obtain oligo-lysine polycationic lipids was
also proposed. Earlier, the method of SPOC was also applied for the synthesis of a
library of various monofunctionalized polyamines that were consequently coupled
to a lipid to produce geometrically varied lipopolyamines [229] . The effect of side-
chain modification in structure on transfection activity of this lipopolyamine was
evaluated by presenting a series of lipopolyamines bearing a variety of side chains
for different application: biotinyl, arachidonyl or glycosyl for targeting, rhodaminyl
for labeling, and guanidyl for stabilizing lipid-DNA complexes [230] .